The present disclosure relates to video call quality between terminals using a Packet-Switched (PS) network, and more particularly to alleviating video degradation during a video call.
Unlike a Circuit-Switched (CS) 2G or 3G network, Long-Term Evolution (LTE) (post-4G communication protocol) supports PS network. However, even with LTE, voice calls can still use 3G networks. For example, if a voice call is received while a User Equipment (UE) is accessing a 4G network, a Circuit Switched Fall-Back (CSFB) technique will disconnect from the 4G network and connect to a 3G network.
Additionally, Voice over LTE (VoLTE) supports high-quality voice calls in a broader bandwidth of LTE and VoLTE based video calls with high definition (HD) video quality (1280×720 pixels, 30 fps) is also supported. The HD video quality is better than the quality in an existing CS video call (for example, Common Intermediate Format (CIF) 353×288 pixels, 15 fps).
The CSFB technique is a method of making voice calls where a mobile communication carrier inserts CS call paging information between LTE signals in a core network and provides it to a UE. However, with Single Radio LTE (SRLTE) UE, when the UE checks 3G network for CS paging information (tune-away) the SRLTE UE must stop communicating on the LTE network. Accordingly, LTE data throughput may deteriorate during the tune-away periods on an SRLTE UE.
According to the 3rd Generation Partnership Project (3GPP) TS 44.018 specifications, a CS paging period may have a minimum time of 470 ms and a maximum time of 2.12 s. The CS paging period is determined by the parameter BS_PA_FRMS set in each CELL. In each CS paging period, the LTE connection is disconnected from about 15 ms to about 30 ms to tune-away for the UE to receive and parse a paging message. That is, in the case of a terminal supporting a SRLTE method, during a video call using VoLTE the video quality may deteriorate due to the 15-30 ms tune-away every 470 ms˜2.12 s.